diff options
Diffstat (limited to 'time/mktime.c')
| -rw-r--r-- | time/mktime.c | 30 |
1 files changed, 21 insertions, 9 deletions
diff --git a/time/mktime.c b/time/mktime.c index ce691c8451..7b93f1d42e 100644 --- a/time/mktime.c +++ b/time/mktime.c @@ -256,14 +256,14 @@ __mktime_internal (tp, convert, offset) struct tm *(*convert) __P ((const time_t *, struct tm *)); time_t *offset; { - time_t t, dt, t0; + time_t t, dt, t0, t1, t2; struct tm tm; /* The maximum number of probes (calls to CONVERT) should be enough to handle any combinations of time zone rule changes, solar time, - and leap seconds. POSIX.1 prohibits leap seconds, but some hosts - have them anyway. */ - int remaining_probes = 4; + leap seconds, and oscillations around a spring-forward gap. + POSIX.1 prohibits leap seconds, but some hosts have them anyway. */ + int remaining_probes = 6; /* Time requested. Copy it in case CONVERT modifies *TP; this can occur if TP is localtime's returned value and CONVERT is localtime. */ @@ -309,15 +309,27 @@ __mktime_internal (tp, convert, offset) tm.tm_yday = tm.tm_hour = tm.tm_min = tm.tm_sec = 0; t0 = ydhms_tm_diff (year, yday, hour, min, sec, &tm); - for (t = t0 + *offset; + for (t = t1 = t2 = t0 + *offset; (dt = ydhms_tm_diff (year, yday, hour, min, sec, ranged_convert (convert, &t, &tm))); - t += dt) - if (--remaining_probes == 0) + t1 = t2, t2 = t, t += dt) + if (t == t1 && t != t2 + && (isdst < 0 || tm.tm_isdst < 0 + || (isdst != 0) != (tm.tm_isdst != 0))) + /* We can't possibly find a match, as we are oscillating + between two values. The requested time probably falls + within a spring-forward gap of size DT. Follow the common + practice in this case, which is to return a time that is DT + away from the requested time, preferring a time whose + tm_isdst differs from the requested value. In practice, + this is more useful than returning -1. */ + break; + else if (--remaining_probes == 0) return -1; - /* Check whether tm.tm_isdst has the requested value, if any. */ - if (0 <= isdst && 0 <= tm.tm_isdst) + /* If we have a match, check whether tm.tm_isdst has the requested + value, if any. */ + if (dt == 0 && 0 <= isdst && 0 <= tm.tm_isdst) { int dst_diff = (isdst != 0) - (tm.tm_isdst != 0); if (dst_diff) |